Disruptive behavior disorders are characterized by antisocial, aggressive behaviors. Externalizing problems are the most commonly diagnosed mental health problems of childhood. They tend to be stable over time, resistant to treatment, and linked to psychiatric disorders in adolescence and adulthood. Early onset aggression is a precursor of life-course persistent antisocial behavior. Little is known, however, about constitutional and environmental factors, and their interactions, that contribute to different developmental outcomes. Eighty-two 4-5 year-old children at low, moderate or high risk for later disruptive behavior disorders (based on initial levels of externalizing problems), have been studied at three subsequent time points; 6-7, 8-10, and 12-13 years. Social, emotional, cognitive, and physiological areas of child functioning are examined, in conjunction with socialization experiences. The goal is to identify key factors that contribute to continuity and change over time in young childrens behavioral problems. The problems of preschool children have shown marked stability over time, indicating their chronic, pervasive nature. Adaptive child- rearing practices that contribute to decreases in behavior problems over time have been identified. Positive parenting practices may have a direct effect in reducing childrens antisocial behavior. They also may have an indirect effect by helping to preserve childrens empathy over time. Deficits in concern for others well-being have long been held as one of the hallmarks of antisocial behavior disorders. By age 7, many of the children with clinical problems studied here have begun to show a decline in empathic, caring behaviors. Others, however, who had shown similar initial levels of problem behavior, continued to show concern; and their antisocial behavior patterns decreased with age. Supportive sibling relationships also were associated with a decline in behavior problems over time, indicating another aspect of socialization that may influence long-term development. - antisocial development; early onset aggression; disruptive behavior disorders - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only